diff --git a/crypto/comp/c_zlib.c b/crypto/comp/c_zlib.c
index 6731af8b0..9c32614d3 100644
--- a/crypto/comp/c_zlib.c
+++ b/crypto/comp/c_zlib.c
@@ -404,8 +404,9 @@ COMP_METHOD *COMP_zlib(void)
 void COMP_zlib_cleanup(void)
 {
 #ifdef ZLIB_SHARED
-    if (zlib_dso)
+    if (zlib_dso != NULL)
         DSO_free(zlib_dso);
+    zlib_dso = NULL;
 #endif
 }